--- stack/stack.c	2002/03/10 13:00:01	1.101
+++ stack/stack.c	2002/03/12 14:53:19	1.105
@@ -20,6 +20,9 @@
 	     Teddy Hogeborn <teddy@fukt.bth.se>
 */
 
+#define CAR(X) X->content.c->car
+#define CDR(X) X->content.c->cdr
+
 /* printf, sscanf, fgets, fprintf, fopen, perror */
 #include <stdio.h>
 /* exit, EXIT_SUCCESS, malloc, free */
@@ -70,16 +73,13 @@
 /* Discard the top element of the stack. */
 extern void toss(environment *env)
 {
-  stackitem *temp= env->head;
-
-  if((env->head)==NULL) {
+  if(env->head==NULL) {
     printerr("Too Few Arguments");
     env->err= 1;
     return;
   }
   
-  env->head= env->head->next;	/* Remove the top stack item */
-  free(temp);			/* Free the old top stack item */
+  env->head= CDR(env->head); /* Remove the top stack item */
 }
 
 /* Returns a pointer to a pointer to an element in the hash table. */
@@ -121,6 +121,7 @@
 
   nitem->item= nval;
   nitem->next= env->gc_ref;
+
   env->gc_ref= nitem;
 
   env->gc_count += sizeof(value);
@@ -134,20 +135,14 @@
    Marked values are not collected by the GC. */
 inline void gc_mark(value *val)
 {
-  stackitem *iterator;
-
-  if(val->gc.flag.mark)
+  if(val==NULL || val->gc.flag.mark)
     return;
 
   val->gc.flag.mark= 1;
 
-  if(val->type==list) {
-    iterator= val->content.ptr;
-
-    while(iterator!=NULL) {
-      gc_mark(iterator->item);
-      iterator= iterator->next;
-    }
+  if(val->type==tcons) {
+    gc_mark(CAR(val));
+    gc_mark(CDR(val));
   }
 }
 
@@ -162,38 +157,31 @@
 /* Start GC */
 extern void gc_init(environment *env)
 {
-  stackitem *new_head= NULL, *titem, *iterator;
+  stackitem *new_head= NULL, *titem;
+  cons *iterator;
   symbol *tsymb;
   int i;
 
-  if(env->interactive){
+  if(env->interactive)
     printf("Garbage collecting.");
-  }
 
   /* Mark values on stack */
-  iterator= env->head;
-  while(iterator!=NULL) {
-    gc_mark(iterator->item);
-    iterator= iterator->next;
-  }
+  gc_mark(env->head);
 
-  if(env->interactive){
+  if(env->interactive)
     printf(".");
-  }
+
 
   /* Mark values in hashtable */
-  for(i= 0; i<HASHTBLSIZE; i++) {
-    tsymb= env->symbols[i];
-    while(tsymb!=NULL) {
+  for(i= 0; i<HASHTBLSIZE; i++)
+    for(tsymb= env->symbols[i]; tsymb!=NULL; tsymb= tsymb->next)
       if (tsymb->val != NULL)
 	gc_mark(tsymb->val);
-      tsymb= tsymb->next;
-    }
-  }
 
-  if(env->interactive){
+
+  if(env->interactive)
     printf(".");
-  }
+
 
   env->gc_count= 0;
 
@@ -201,30 +189,21 @@
 
     if(!(env->gc_ref->item->gc.no_gc)){ /* neither mark nor protect */
 
-      switch(env->gc_ref->item->type) {	/* Remove content */
-      case string:
+      if(env->gc_ref->item->type==string) /* Remove content */
 	free(env->gc_ref->item->content.ptr);
-	break;
-      case list:
-	while(env->gc_ref->item->content.ptr!=NULL) {
-	  titem= env->gc_ref->item->content.ptr;
-	  env->gc_ref->item->content.ptr= titem->next;
-	  free(titem);
-	}
-      default:
-      }
+
       free(env->gc_ref->item);	/* Remove from gc_ref */
       titem= env->gc_ref->next;
       free(env->gc_ref);	/* Remove value */
       env->gc_ref= titem;
       continue;
-    } else {
-      env->gc_count += sizeof(value);
-      if(env->gc_ref->item->type == string)
-	env->gc_count += strlen(env->gc_ref->item->content.ptr);
-    }
+    } 
+
+    /* Keep values */     
+    env->gc_count += sizeof(value);
+    if(env->gc_ref->item->type==string)
+      env->gc_count += strlen(env->gc_ref->item->content.ptr);
     
-    /* Keep values */
     titem= env->gc_ref->next;
     env->gc_ref->next= new_head;
     new_head= env->gc_ref;
@@ -237,59 +216,49 @@
 
   env->gc_ref= new_head;
 
-  if(env->interactive){
+  if(env->interactive)
     printf("done\n");
-  }
 
 }
 
 /* Protect values from GC */
 void protect(value *val)
 {
-  stackitem *iterator;
-
-  if(val->gc.flag.protect)
+  if(val==NULL || val->gc.flag.protect)
     return;
 
   val->gc.flag.protect= 1;
 
-  if(val->type==list) {
-    iterator= val->content.ptr;
-
-    while(iterator!=NULL) {
-      protect(iterator->item);
-      iterator= iterator->next;
-    }
+  if(val->type==tcons) {
+    protect(CAR(val));
+    protect(CDR(val));
   }
 }
 
 /* Unprotect values from GC */
 void unprotect(value *val)
 {
-  stackitem *iterator;
-
-  if(!(val->gc.flag.protect))
+  if(val==NULL || !(val->gc.flag.protect))
     return;
 
   val->gc.flag.protect= 0;
 
-  if(val->type==list) {
-    iterator= val->content.ptr;
-
-    while(iterator!=NULL) {
-      unprotect(iterator->item);
-      iterator= iterator->next;
-    }
+  if(val->type==tcons) {
+    unprotect(CAR(val));
+    unprotect(CDR(val));
   }
 }
 
 /* Push a value onto the stack */
 void push_val(environment *env, value *val)
 {
-  stackitem *new_item= malloc(sizeof(stackitem));
-  new_item->item= val;
-  new_item->next= env->head;
-  env->head= new_item;
+  value *new_value= new_val(env);
+
+  new_value->content.c= malloc(sizeof(cons));
+  new_value->type= tcons;
+  CAR(new_value)= val;
+  CDR(new_value)= env->head;
+  env->head= new_value;
 }
 
 /* Push an integer onto the stack */
@@ -352,19 +321,20 @@
 {
   char *new_string;
 
-  if((env->head)==NULL) {
+  if(env->head==NULL) {
     printerr("Too Few Arguments");
     env->err= 1;
     return;
   }
 
-  if(env->head->item->type!=string) {
+  if(CAR(env->head)->type!=string) {
     printerr("Bad Argument Type");
     env->err= 2;
     return;
   }
 
-  new_string= mangle_str((const char *)(env->head->item->content.ptr));
+  new_string= 
+    mangle_str((const char *)(CAR(env->head)->content.ptr));
 
   toss(env);
   if(env->err) return;
@@ -450,12 +420,13 @@
 {
   int typenum;
 
-  if((env->head)==NULL) {
+  if(env->head==NULL) {
     printerr("Too Few Arguments");
-    env->err=1;
+    env->err= 1;
     return;
   }
-  typenum=env->head->item->type;
+
+  typenum= CAR(env->head)->type;
   toss(env);
   switch(typenum){
   case integer:
@@ -473,42 +444,42 @@
   case func:
     push_sym(env, "function");
     break;
-  case list:
+  case tcons:
     push_sym(env, "list");
     break;
   }
 }    
 
 /* Prints the top element of the stack. */
-void print_h(stackitem *stack_head, int noquote)
+void print_h(value *stack_head, int noquote)
 {
-  switch(stack_head->item->type) {
+  switch(CAR(stack_head)->type) {
   case integer:
-    printf("%d", stack_head->item->content.i);
+    printf("%d", CAR(stack_head)->content.i);
     break;
   case tfloat:
-    printf("%f", stack_head->item->content.f);
+    printf("%f", CAR(stack_head)->content.f);
     break;
   case string:
     if(noquote)
-      printf("%s", (char*)stack_head->item->content.ptr);
+      printf("%s", (char*)CAR(stack_head)->content.ptr);
     else
-      printf("\"%s\"", (char*)stack_head->item->content.ptr);
+      printf("\"%s\"", (char*)CAR(stack_head)->content.ptr);
     break;
   case symb:
-    printf("%s", ((symbol *)(stack_head->item->content.ptr))->id);
+    printf("%s", CAR(stack_head)->content.sym->id);
     break;
   case func:
-    printf("#<function %p>", (funcp)(stack_head->item->content.ptr));
+    printf("#<function %p>", (funcp)(CAR(stack_head)->content.ptr));
     break;
-  case list:
+  case tcons:
     /* A list is just a stack, so make stack_head point to it */
-    stack_head=(stackitem *)(stack_head->item->content.ptr);
+    stack_head= CAR(stack_head);
     printf("[ ");
     while(stack_head != NULL) {
       print_h(stack_head, noquote);
       printf(" ");
-      stack_head=stack_head->next;
+      stack_head= CDR(stack_head);
     }
     printf("]");
     break;
@@ -519,7 +490,7 @@
 {
   if(env->head==NULL) {
     printerr("Too Few Arguments");
-    env->err=1;
+    env->err= 1;
     return;
   }
   print_h(env->head, 0);
@@ -538,7 +509,7 @@
 {
   if(env->head==NULL) {
     printerr("Too Few Arguments");
-    env->err=1;
+    env->err= 1;
     return;
   }
   print_h(env->head, 1);
@@ -553,10 +524,10 @@
 }
 
 /* Only to be called by function printstack. */
-void print_st(stackitem *stack_head, long counter)
+void print_st(value *stack_head, long counter)
 { 
-  if(stack_head->next != NULL)
-    print_st(stack_head->next, counter+1);
+  if(CDR(stack_head) != NULL)
+    print_st(CDR(stack_head), counter+1);
   printf("%ld: ", counter);
   print_h(stack_head, 0);
   nl();
@@ -576,34 +547,34 @@
 /* Swap the two top elements on the stack. */
 extern void swap(environment *env)
 {
-  stackitem *temp= env->head;
+  value *temp= env->head;
   
-  if(env->head==NULL || env->head->next==NULL) {
+  if(env->head==NULL || CDR(env->head)==NULL) {
     printerr("Too Few Arguments");
     env->err=1;
     return;
   }
 
-  env->head= env->head->next;
-  temp->next= env->head->next;
-  env->head->next= temp;
+  env->head= CDR(env->head);
+  CDR(temp)= CDR(env->head);
+  CDR(env->head)= temp;
 } 
 
 /* Rotate the first three elements on the stack. */
 extern void rot(environment *env)
 {
-  stackitem *temp= env->head;
+  value *temp= env->head;
   
-  if(env->head==NULL || env->head->next==NULL
-      || env->head->next->next==NULL) {
+  if(env->head==NULL || CDR(env->head)==NULL
+     || CDR(CDR(env->head))==NULL) {
     printerr("Too Few Arguments");
-    env->err=1;
+    env->err= 1;
     return;
   }
-
-  env->head= env->head->next->next;
-  temp->next->next= env->head->next;
-  env->head->next= temp;
+  
+  env->head= CDR(CDR(env->head));
+  CDR(CDR(temp))= CDR(env->head);
+  CDR(env->head)= temp;
 }
 
 /* Recall a value from a symbol, if bound */
@@ -611,22 +582,22 @@
 {
   value *val;
 
-  if(env->head == NULL) {
+  if(env->head==NULL) {
     printerr("Too Few Arguments");
-    env->err=1;
+    env->err= 1;
     return;
   }
 
-  if(env->head->item->type!=symb) {
+  if(CAR(env->head)->type!=symb) {
     printerr("Bad Argument Type");
-    env->err=2;
+    env->err= 2;
     return;
   }
 
-  val=((symbol *)(env->head->item->content.ptr))->val;
+  val= CAR(env->head)->content.sym->val;
   if(val == NULL){
     printerr("Unbound Variable");
-    env->err=3;
+    env->err= 3;
     return;
   }
   protect(val);
@@ -643,7 +614,7 @@
 {
   funcp in_func;
   value* temp_val;
-  stackitem* iterator;
+  value* iterator;
 
  eval_start:
 
@@ -651,50 +622,56 @@
 
   if(env->head==NULL) {
     printerr("Too Few Arguments");
-    env->err=1;
+    env->err= 1;
     return;
   }
 
-  switch(env->head->item->type) {
+  switch(CAR(env->head)->type) {
     /* if it's a symbol */
   case symb:
     rcl(env);			/* get its contents */
     if(env->err) return;
-    if(env->head->item->type!=symb){ /* don't recurse symbols */
+    if(CAR(env->head)->type!=symb){ /* don't recurse symbols */
       goto eval_start;
     }
     return;
 
     /* If it's a lone function value, run it */
   case func:
-    in_func= (funcp)(env->head->item->content.ptr);
+    in_func= (funcp)(CAR(env->head)->content.ptr);
     toss(env); 
     if(env->err) return;
     return in_func(env);
 
     /* If it's a list */
-  case list:
-    temp_val= env->head->item;
+  case tcons:
+    temp_val= CAR(env->head);
     protect(temp_val);
 
     toss(env); if(env->err) return;
-    iterator= (stackitem*)temp_val->content.ptr;
+    iterator= temp_val;
     
     while(iterator!=NULL) {
-      push_val(env, iterator->item);
+      push_val(env, CAR(iterator));
       
-      if(env->head->item->type==symb
-	 && (((symbol*)(env->head->item->content.ptr))->id[0] == ';')) {
+      if(CAR(env->head)->type==symb
+	 && CAR(env->head)->content.sym->id[0]==';') {
 	toss(env);
 	if(env->err) return;
 	
-	if(iterator->next == NULL){
+	if(CDR(iterator)==NULL){
 	  goto eval_start;
 	}
 	eval(env);
 	if(env->err) return;
       }
-      iterator= iterator->next;
+      if (CDR(iterator)->type == tcons) 
+	iterator= CDR(iterator);
+      else {
+	printerr("Bad Argument Type"); /* Improper list */
+	env->err= 2;
+	return;
+      }
     }
     unprotect(temp_val);
     return;
@@ -707,77 +684,68 @@
 /* Reverse (flip) a list */
 extern void rev(environment *env)
 {
-  stackitem *old_head, *new_head, *item;
+  value *old_head, *new_head, *item;
 
-  if((env->head)==NULL) {
+  if(env->head==NULL) {
     printerr("Too Few Arguments");
     env->err= 1;
     return;
   }
 
-  if(env->head->item->type!=list) {
+  if(CAR(env->head)->type!=tcons) {
     printerr("Bad Argument Type");
     env->err= 2;
     return;
   }
 
-  old_head= (stackitem *)(env->head->item->content.ptr);
+  old_head= CAR(env->head);
   new_head= NULL;
-  while(old_head != NULL){
+  while(old_head!=NULL) {
     item= old_head;
-    old_head= old_head->next;
-    item->next= new_head;
+    old_head= CDR(old_head);
+    CDR(item)= new_head;
     new_head= item;
   }
-  env->head->item->content.ptr= new_head;
+  CAR(env->head)= new_head;
 }
 
 /* Make a list. */
 extern void pack(environment *env)
 {
-  stackitem *iterator, *temp;
-  value *pack;
+  value *iterator, *temp;
 
   iterator= env->head;
-  pack= new_val(env);
-  protect(pack);
-
   if(iterator==NULL
-     || (iterator->item->type==symb
-     && ((symbol*)(iterator->item->content.ptr))->id[0]=='[')) {
+     || (CAR(iterator)->type==symb
+     && CAR(iterator)->content.sym->id[0]=='[')) {
     temp= NULL;
     toss(env);
   } else {
     /* Search for first delimiter */
-    while(iterator->next!=NULL
-	  && (iterator->next->item->type!=symb
-	  || ((symbol*)(iterator->next->item->content.ptr))->id[0]!='['))
-      iterator= iterator->next;
+    while(CDR(iterator)!=NULL
+	  && (CAR(CDR(iterator))->type!=symb
+	   || CAR(CDR(iterator))->content.sym->id[0]!='['))
+      iterator= CDR(iterator);
     
     /* Extract list */
     temp= env->head;
-    env->head= iterator->next;
-    iterator->next= NULL;
+    env->head= CDR(iterator);
+    CDR(iterator)= NULL;
 
-    pack->type= list;
-    pack->content.ptr= temp;
-    
     if(env->head!=NULL)
       toss(env);
   }
 
   /* Push list */
 
-  push_val(env, pack);
+  push_val(env, temp);
   rev(env);
-
-  unprotect(pack);
 }
 
 /* Relocate elements of the list on the stack. */
 extern void expand(environment *env)
 {
-  stackitem *temp, *new_head;
+  value *temp, *new_head;
 
   /* Is top element a list? */
   if(env->head==NULL) {
@@ -785,7 +753,8 @@
     env->err= 1;
     return;
   }
-  if(env->head->item->type!=list) {
+
+  if(CAR(env->head)->type!=tcons) {
     printerr("Bad Argument Type");
     env->err= 2;
     return;
@@ -797,16 +766,23 @@
     return;
 
   /* The first list element is the new stack head */
-  new_head= temp= env->head->item->content.ptr;
+  new_head= temp= CAR(env->head);
 
   toss(env);
 
   /* Find the end of the list */
-  while(temp->next!=NULL)
-    temp= temp->next;
+  while(CDR(temp)->content.ptr != NULL) {
+    if (CDR(temp)->type == tcons)
+      temp= CDR(temp);
+    else {
+      printerr("Bad Argument Type"); /* Improper list */
+      env->err= 2;
+      return;
+    }
+  }
 
   /* Connect the tail of the list with the old stack head */
-  temp->next= env->head;
+  CDR(temp)= env->head;
   env->head= new_head;		/* ...and voila! */
 
 }
@@ -815,21 +791,18 @@
 extern void eq(environment *env)
 {
   void *left, *right;
-  int result;
 
-  if((env->head)==NULL || env->head->next==NULL) {
+  if(env->head==NULL || CDR(env->head)==NULL) {
     printerr("Too Few Arguments");
     env->err= 1;
     return;
   }
 
-  left= env->head->item->content.ptr;
-  swap(env);
-  right= env->head->item->content.ptr;
-  result= (left==right);
-  
+  left= CAR(env->head)->content.ptr;
+  right= CAR(CDR(env->head))->content.ptr;
   toss(env); toss(env);
-  push_int(env, result);
+
+  push_int(env, left==right);
 }
 
 /* Negates the top element on the stack. */
@@ -837,19 +810,19 @@
 {
   int val;
 
-  if((env->head)==NULL) {
+  if(env->head==NULL) {
     printerr("Too Few Arguments");
     env->err= 1;
     return;
   }
 
-  if(env->head->item->type!=integer) {
+  if(CAR(env->head)->type!=integer) {
     printerr("Bad Argument Type");
     env->err= 2;
     return;
   }
 
-  val= env->head->item->content.i;
+  val= CAR(env->head)->content.i;
   toss(env);
   push_int(env, !val);
 }
@@ -868,23 +841,23 @@
   symbol *sym;
 
   /* Needs two values on the stack, the top one must be a symbol */
-  if(env->head==NULL || env->head->next==NULL) {
+  if(env->head==NULL || CDR(env->head)==NULL) {
     printerr("Too Few Arguments");
     env->err= 1;
     return;
   }
 
-  if(env->head->item->type!=symb) {
+  if(CAR(env->head)->type!=symb) {
     printerr("Bad Argument Type");
     env->err= 2;
     return;
   }
 
   /* long names are a pain */
-  sym= env->head->item->content.ptr;
+  sym= CAR(env->head)->content.ptr;
 
   /* Bind the symbol to the value */
-  sym->val= env->head->next->item;
+  sym->val= CAR(CDR(env->head));
 
   toss(env); toss(env);
 } 
@@ -953,21 +926,21 @@
 extern void forget(environment *env)
 {
   char* sym_id;
-  stackitem *stack_head= env->head;
+  value *stack_head= env->head;
 
   if(stack_head==NULL) {
     printerr("Too Few Arguments");
-    env->err=1;
+    env->err= 1;
     return;
   }
   
-  if(stack_head->item->type!=symb) {
+  if(CAR(stack_head)->type!=symb) {
     printerr("Bad Argument Type");
-    env->err=2;
+    env->err= 2;
     return;
   }
 
-  sym_id= ((symbol*)(stack_head->item->content.ptr))->id;
+  sym_id= CAR(stack_head)->content.sym->id;
   toss(env);
 
   return forget_sym(hash(env->symbols, sym_id));
@@ -1016,7 +989,7 @@
   }
 
   if(myenv.interactive) {
-    printf("Stack version $Revision: 1.101 $\n\
+    printf("Stack version $Revision: 1.105 $\n\
 Copyright (C) 2002  Mats Alritzson and Teddy Hogeborn\n\
 Stack comes with ABSOLUTELY NO WARRANTY; for details type `warranty;'.\n\
 This is free software, and you are welcome to redistribute it\n\
@@ -1039,8 +1012,9 @@
     if (myenv.err==4) {
       return EXIT_SUCCESS;	/* EOF */
     } else if(myenv.head!=NULL
-	      && myenv.head->item->type==symb
-	      && ((symbol*)(myenv.head->item->content.ptr))->id[0]==';') {
+	      && CAR(myenv.head)->type==symb
+	      && CAR(myenv.head)->content.sym->id[0]
+	      ==';') {
       toss(&myenv); 		/* No error check in main */
       eval(&myenv);
     }
@@ -1059,16 +1033,16 @@
   char* new_string;
   value *a_val, *b_val;
 
-  if((env->head)==NULL || env->head->next==NULL) {
+  if(env->head==NULL || CDR(env->head)==NULL) {
     printerr("Too Few Arguments");
     env->err= 1;
     return;
   }
 
-  if(env->head->item->type==string
-     && env->head->next->item->type==string) {
-    a_val= env->head->item;
-    b_val= env->head->next->item;
+  if(CAR(env->head)->type==string
+     && CAR(CDR(env->head))->type==string) {
+    a_val= CAR(env->head);
+    b_val= CAR(CDR(env->head));
     protect(a_val); protect(b_val);
     toss(env); if(env->err) return;
     toss(env); if(env->err) return;
@@ -1083,44 +1057,44 @@
     return;
   }
   
-  if(env->head->item->type==integer
-     && env->head->next->item->type==integer) {
-    a=env->head->item->content.i;
+  if(CAR(env->head)->type==integer
+     && CAR(CDR(env->head))->type==integer) {
+    a= CAR(env->head)->content.i;
     toss(env); if(env->err) return;
-    b=env->head->item->content.i;
+    b= CAR(env->head)->content.i;
     toss(env); if(env->err) return;
     push_int(env, b+a);
 
     return;
   }
 
-  if(env->head->item->type==tfloat
-     && env->head->next->item->type==tfloat) {
-    fa= env->head->item->content.f;
+  if(CAR(env->head)->type==tfloat
+     && CAR(CDR(env->head))->type==tfloat) {
+    fa= CAR(env->head)->content.f;
     toss(env); if(env->err) return;
-    fb= env->head->item->content.f;
+    fb= CAR(env->head)->content.f;
     toss(env); if(env->err) return;
     push_float(env, fb+fa);
     
     return;
   }
 
-  if(env->head->item->type==tfloat
-     && env->head->next->item->type==integer) {
-    fa= env->head->item->content.f;
+  if(CAR(env->head)->type==tfloat
+     && CAR(CDR(env->head))->type==integer) {
+    fa= CAR(env->head)->content.f;
     toss(env); if(env->err) return;
-    b= env->head->item->content.i;
+    b= CAR(env->head)->content.i;
     toss(env); if(env->err) return;
     push_float(env, b+fa);
     
     return;
   }
 
-  if(env->head->item->type==integer
-     && env->head->next->item->type==tfloat) {
-    a= env->head->item->content.i;
+  if(CAR(env->head)->type==integer
+     && CAR(CDR(env->head))->type==tfloat) {
+    a= CAR(env->head)->content.i;
     toss(env); if(env->err) return;
-    fb= env->head->item->content.f;
+    fb= CAR(env->head)->content.f;
     toss(env); if(env->err) return;
     push_float(env, fb+a);
 
@@ -1137,50 +1111,50 @@
   int a, b;
   float fa, fb;
 
-  if((env->head)==NULL || env->head->next==NULL) {
+  if(env->head==NULL || CDR(env->head)==NULL) {
     printerr("Too Few Arguments");
     env->err=1;
     return;
   }
   
-  if(env->head->item->type==integer
-     && env->head->next->item->type==integer) {
-    a=env->head->item->content.i;
+  if(CAR(env->head)->type==integer
+     && CAR(CDR(env->head))->type==integer) {
+    a= CAR(env->head)->content.i;
     toss(env); if(env->err) return;
-    b=env->head->item->content.i;
+    b= CAR(env->head)->content.i;
     toss(env); if(env->err) return;
     push_int(env, b-a);
 
     return;
   }
 
-  if(env->head->item->type==tfloat
-     && env->head->next->item->type==tfloat) {
-    fa= env->head->item->content.f;
+  if(CAR(env->head)->type==tfloat
+     && CAR(CDR(env->head))->type==tfloat) {
+    fa= CAR(env->head)->content.f;
     toss(env); if(env->err) return;
-    fb= env->head->item->content.f;
+    fb= CAR(env->head)->content.f;
     toss(env); if(env->err) return;
     push_float(env, fb-fa);
     
     return;
   }
 
-  if(env->head->item->type==tfloat
-     && env->head->next->item->type==integer) {
-    fa= env->head->item->content.f;
+  if(CAR(env->head)->type==tfloat
+     && CAR(CDR(env->head))->type==integer) {
+    fa= CAR(env->head)->content.f;
     toss(env); if(env->err) return;
-    b= env->head->item->content.i;
+    b= CAR(env->head)->content.i;
     toss(env); if(env->err) return;
     push_float(env, b-fa);
     
     return;
   }
 
-  if(env->head->item->type==integer
-     && env->head->next->item->type==tfloat) {
-    a= env->head->item->content.i;
+  if(CAR(env->head)->type==integer
+     && CAR(CDR(env->head))->type==tfloat) {
+    a= CAR(env->head)->content.i;
     toss(env); if(env->err) return;
-    fb= env->head->item->content.f;
+    fb= CAR(env->head)->content.f;
     toss(env); if(env->err) return;
     push_float(env, fb-a);
 
@@ -1197,50 +1171,50 @@
   int a, b;
   float fa, fb;
 
-  if((env->head)==NULL || env->head->next==NULL) {
+  if(env->head==NULL || CDR(env->head)==NULL) {
     printerr("Too Few Arguments");
-    env->err=1;
+    env->err= 1;
     return;
   }
   
-  if(env->head->item->type==integer
-     && env->head->next->item->type==integer) {
-    a=env->head->item->content.i;
+  if(CAR(env->head)->type==integer
+     && CAR(CDR(env->head))->type==integer) {
+    a= CAR(env->head)->content.i;
     toss(env); if(env->err) return;
-    b=env->head->item->content.i;
+    b= CAR(env->head)->content.i;
     toss(env); if(env->err) return;
     push_int(env, b>a);
 
     return;
   }
 
-  if(env->head->item->type==tfloat
-     && env->head->next->item->type==tfloat) {
-    fa= env->head->item->content.f;
+  if(CAR(env->head)->type==tfloat
+     && CAR(CDR(env->head))->type==tfloat) {
+    fa= CAR(env->head)->content.f;
     toss(env); if(env->err) return;
-    fb= env->head->item->content.f;
+    fb= CAR(env->head)->content.f;
     toss(env); if(env->err) return;
     push_int(env, fb>fa);
     
     return;
   }
 
-  if(env->head->item->type==tfloat
-     && env->head->next->item->type==integer) {
-    fa= env->head->item->content.f;
+  if(CAR(env->head)->type==tfloat
+     && CAR(CDR(env->head))->type==integer) {
+    fa= CAR(env->head)->content.f;
     toss(env); if(env->err) return;
-    b= env->head->item->content.i;
+    b= CAR(env->head)->content.i;
     toss(env); if(env->err) return;
     push_int(env, b>fa);
     
     return;
   }
 
-  if(env->head->item->type==integer
-     && env->head->next->item->type==tfloat) {
-    a= env->head->item->content.i;
+  if(CAR(env->head)->type==integer
+     && CAR(CDR(env->head))->type==tfloat) {
+    a= CAR(env->head)->content.i;
     toss(env); if(env->err) return;
-    fb= env->head->item->content.f;
+    fb= CAR(env->head)->content.f;
     toss(env); if(env->err) return;
     push_int(env, fb>a);
 
@@ -1248,7 +1222,7 @@
   }
 
   printerr("Bad Argument Type");
-  env->err=2;
+  env->err= 2;
 }
 
 /* "<" */
@@ -1275,9 +1249,11 @@
 /* Return copy of a value */
 value *copy_val(environment *env, value *old_value)
 {
-  stackitem *old_item, *new_item, *prev_item;
   value *new_value;
 
+  if(old_value==NULL)
+    return NULL;
+
   protect(old_value);
   new_value= new_val(env);
   protect(new_value);
@@ -1294,24 +1270,12 @@
     (char *)(new_value->content.ptr)= 
       strdup((char *)(old_value->content.ptr));
     break;
-  case list:
-    new_value->content.ptr= NULL;
-
-    prev_item= NULL;
-    old_item= (stackitem*)(old_value->content.ptr);
+  case tcons:
+    new_value= NULL;
 
-    while(old_item != NULL) {	/* While list is not empty */
-      new_item= malloc(sizeof(stackitem));
-      new_item->item= copy_val(env, old_item->item); /* recurse */
-      new_item->next= NULL;
-      if(prev_item != NULL)	/* If this wasn't the first item */
-	prev_item->next= new_item; /* point the previous item to the
-                                     new item */
-      else
-	new_value->content.ptr= new_item;
-      old_item= old_item->next;
-      prev_item= new_item;
-    }	  
+    new_value->content.c= malloc(sizeof(cons));
+    CAR(new_value)= copy_val(env, CAR(old_value)); /* recurse */
+    CDR(new_value)= copy_val(env, CDR(old_value)); /* recurse */
     break;
   }
 
@@ -1323,12 +1287,12 @@
 /* "dup"; duplicates an item on the stack */
 extern void sx_647570(environment *env)
 {
-  if((env->head)==NULL) {
+  if(env->head==NULL) {
     printerr("Too Few Arguments");
     env->err= 1;
     return;
   }
-  push_val(env, copy_val(env, env->head->item));
+  push_val(env, copy_val(env, CAR(env->head)));
 }
 
 /* "if", If-Then */
@@ -1336,22 +1300,22 @@
 {
   int truth;
 
-  if((env->head)==NULL || env->head->next==NULL) {
+  if(env->head==NULL || CDR(env->head)==NULL) {
     printerr("Too Few Arguments");
     env->err= 1;
     return;
   }
 
-  if(env->head->next->item->type != integer) {
+  if(CAR(CDR(env->head))->type != integer) {
     printerr("Bad Argument Type");
-    env->err=2;
+    env->err= 2;
     return;
   }
   
   swap(env);
   if(env->err) return;
   
-  truth=env->head->item->content.i;
+  truth= CAR(env->head)->content.i;
 
   toss(env);
   if(env->err) return;
@@ -1367,23 +1331,23 @@
 {
   int truth;
 
-  if((env->head)==NULL || env->head->next==NULL
-     || env->head->next->next==NULL) {
+  if(env->head==NULL || CDR(env->head)==NULL 
+     || CDR(CDR(env->head))==NULL) {
     printerr("Too Few Arguments");
-    env->err=1;
+    env->err= 1;
     return;
   }
 
-  if(env->head->next->next->item->type != integer) {
+  if(CAR(CDR(CDR(env->head)))->type!=integer) {
     printerr("Bad Argument Type");
-    env->err=2;
+    env->err= 2;
     return;
   }
   
   rot(env);
   if(env->err) return;
   
-  truth=env->head->item->content.i;
+  truth= CAR(env->head)->content.i;
 
   toss(env);
   if(env->err) return;
@@ -1404,17 +1368,17 @@
   int truth;
   value *loop, *test;
 
-  if((env->head)==NULL || env->head->next==NULL) {
+  if(env->head==NULL || CDR(env->head)==NULL) {
     printerr("Too Few Arguments");
-    env->err=1;
+    env->err= 1;
     return;
   }
 
-  loop= env->head->item;
+  loop= CAR(env->head);
   protect(loop);
   toss(env); if(env->err) return;
 
-  test= env->head->item;
+  test= CAR(env->head);
   protect(test);
   toss(env); if(env->err) return;
 
@@ -1422,13 +1386,13 @@
     push_val(env, test);
     eval(env);
     
-    if(env->head->item->type != integer) {
+    if(CAR(env->head)->type != integer) {
       printerr("Bad Argument Type");
       env->err= 2;
       return;
     }
     
-    truth= env->head->item->content.i;
+    truth= CAR(env->head)->content.i;
     toss(env); if(env->err) return;
     
     if(truth) {
@@ -1450,28 +1414,28 @@
   value *loop;
   int foo1, foo2;
 
-  if(env->head==NULL || env->head->next==NULL 
-     || env->head->next->next==NULL) {
+  if(env->head==NULL || CDR(env->head)==NULL 
+     || CDR(CDR(env->head))==NULL) {
     printerr("Too Few Arguments");
     env->err= 1;
     return;
   }
 
-  if(env->head->next->item->type!=integer
-     || env->head->next->next->item->type!=integer) {
+  if(CAR(CDR(env->head))->type!=integer
+     || CAR(CDR(CDR(env->head)))->type!=integer) {
     printerr("Bad Argument Type");
     env->err= 2;
     return;
   }
 
-  loop= env->head->item;
+  loop= CAR(env->head);
   protect(loop);
   toss(env); if(env->err) return;
 
-  foo2= env->head->item->content.i;
+  foo2= CAR(env->head)->content.i;
   toss(env); if(env->err) return;
 
-  foo1= env->head->item->content.i;
+  foo1= CAR(env->head)->content.i;
   toss(env); if(env->err) return;
 
   if(foo1<=foo2) {
@@ -1496,35 +1460,41 @@
 extern void foreach(environment *env)
 {  
   value *loop, *foo;
-  stackitem *iterator;
+  value *iterator;
   
-  if((env->head)==NULL || env->head->next==NULL) {
+  if(env->head==NULL || CDR(env->head)==NULL) {
     printerr("Too Few Arguments");
     env->err= 1;
     return;
   }
 
-  if(env->head->next->item->type != list) {
+  if(CAR(CDR(env->head))->type!=tcons) {
     printerr("Bad Argument Type");
     env->err= 2;
     return;
   }
 
-  loop= env->head->item;
+  loop= CAR(env->head);
   protect(loop);
   toss(env); if(env->err) return;
 
-  foo= env->head->item;
+  foo= CAR(env->head);
   protect(foo);
   toss(env); if(env->err) return;
 
-  iterator= foo->content.ptr;
+  iterator= foo;
 
   while(iterator!=NULL) {
-    push_val(env, iterator->item);
+    push_val(env, CAR(iterator));
     push_val(env, loop);
     eval(env); if(env->err) return;
-    iterator= iterator->next;
+    if (iterator->type == tcons){
+      iterator= CDR(iterator);
+    } else {
+      printerr("Bad Argument Type"); /* Improper list */
+      env->err= 2;
+      break;
+    }
   }
   unprotect(loop); unprotect(foo);
 }
@@ -1533,25 +1503,24 @@
 extern void to(environment *env)
 {
   int ending, start, i;
-  stackitem *iterator, *temp;
-  value *pack;
+  value *iterator, *temp;
 
-  if((env->head)==NULL || env->head->next==NULL) {
+  if(env->head==NULL || CDR(env->head)==NULL) {
     printerr("Too Few Arguments");
-    env->err=1;
+    env->err= 1;
     return;
   }
 
-  if(env->head->item->type!=integer 
-     || env->head->next->item->type!=integer) {
+  if(CAR(env->head)->type!=integer 
+     || CAR(CDR(env->head))->type!=integer) {
     printerr("Bad Argument Type");
-    env->err=2;
+    env->err= 2;
     return;
   }
 
-  ending= env->head->item->content.i;
+  ending= CAR(env->head)->content.i;
   toss(env); if(env->err) return;
-  start= env->head->item->content.i;
+  start= CAR(env->head)->content.i;
   toss(env); if(env->err) return;
 
   push_sym(env, "[");
@@ -1565,38 +1534,30 @@
   }
 
   iterator= env->head;
-  pack= new_val(env);
-  protect(pack);
 
   if(iterator==NULL
-     || (iterator->item->type==symb
-     && ((symbol*)(iterator->item->content.ptr))->id[0]=='[')) {
+     || (CAR(iterator)->type==symb
+	 && CAR(iterator)->content.sym->id[0]=='[')) {
     temp= NULL;
     toss(env);
   } else {
     /* Search for first delimiter */
-    while(iterator->next!=NULL
-	  && (iterator->next->item->type!=symb
-	  || ((symbol*)(iterator->next->item->content.ptr))->id[0]!='['))
-      iterator= iterator->next;
+    while(CDR(iterator)!=NULL 
+	  && (CAR(CDR(iterator))->type!=symb
+	      || CAR(CDR(iterator))->content.sym->id[0]!='['))
+      iterator= CDR(iterator);
     
     /* Extract list */
     temp= env->head;
-    env->head= iterator->next;
-    iterator->next= NULL;
+    env->head= CDR(iterator);
+    CDR(iterator)= NULL;
 
-    pack->type= list;
-    pack->content.ptr= temp;
-    
     if(env->head!=NULL)
       toss(env);
   }
 
   /* Push list */
-
-  push_val(env, pack);
-
-  unprotect(pack);
+  push_val(env, temp);
 }
 
 /* Read a string */
@@ -1635,14 +1596,14 @@
     }
     readline(env); if(env->err) return;
 
-    if(((char *)(env->head->item->content.ptr))[0]=='\0'){
+    if(((char *)(CAR(env->head)->content.ptr))[0]=='\0'){
       env->err= 4;		/* "" means EOF */
       return;
     }
     
-    env->in_string= malloc(strlen(env->head->item->content.ptr)+1);
+    env->in_string= malloc(strlen(CAR(env->head)->content.ptr)+1);
     env->free_string= env->in_string; /* Save the original pointer */
-    strcpy(env->in_string, env->head->item->content.ptr);
+    strcpy(env->in_string, CAR(env->head)->content.ptr);
     toss(env); if(env->err) return;
   }
   
@@ -1695,39 +1656,39 @@
 {
   int freq, dur, period, ticks;
 
-  if((env->head)==NULL || env->head->next==NULL) {
+  if(env->head==NULL || CDR(env->head)==NULL) {
     printerr("Too Few Arguments");
-    env->err=1;
+    env->err= 1;
     return;
   }
 
-  if(env->head->item->type!=integer
-     || env->head->next->item->type!=integer) {
+  if(CAR(env->head)->type!=integer
+     || CAR(CDR(env->head))->type!=integer) {
     printerr("Bad Argument Type");
-    env->err=2;
+    env->err= 2;
     return;
   }
 
-  dur=env->head->item->content.i;
+  dur= CAR(env->head)->content.i;
   toss(env);
-  freq=env->head->item->content.i;
+  freq= CAR(env->head)->content.i;
   toss(env);
 
-  period=1193180/freq;		/* convert freq from Hz to period
+  period= 1193180/freq;		/* convert freq from Hz to period
                                    length */
-  ticks=dur*.001193180;		/* convert duration from µseconds to
+  ticks= dur*.001193180;	/* convert duration from µseconds to
 				   timer ticks */
 
 /*    ticks=dur/1000; */
 
-  /*  if (ioctl(STDOUT_FILENO, KDMKTONE, (125<<16) + 0x637)==0) */
+      /*  if (ioctl(STDOUT_FILENO, KDMKTONE, (125<<16) + 0x637)==0) */
   switch (ioctl(STDOUT_FILENO, KDMKTONE, (ticks<<16) | period)){
   case 0:
     usleep(dur);
     return;
   case -1:
     perror("beep");
-    env->err=5;
+    env->err= 5;
     return;
   default:
     abort();
@@ -1739,19 +1700,19 @@
 {
   int dur;
 
-  if((env->head)==NULL) {
+  if(env->head==NULL) {
     printerr("Too Few Arguments");
-    env->err=1;
+    env->err= 1;
     return;
   }
 
-  if(env->head->item->type!=integer) {
+  if(CAR(env->head)->type!=integer) {
     printerr("Bad Argument Type");
-    env->err=2;
+    env->err= 2;
     return;
   }
 
-  dur=env->head->item->content.i;
+  dur= CAR(env->head)->content.i;
   toss(env);
 
   usleep(dur);
@@ -2048,50 +2009,50 @@
   int a, b;
   float fa, fb;
 
-  if((env->head)==NULL || env->head->next==NULL) {
+  if(env->head==NULL || CDR(env->head)==NULL) {
     printerr("Too Few Arguments");
-    env->err=1;
+    env->err= 1;
     return;
   }
   
-  if(env->head->item->type==integer
-     && env->head->next->item->type==integer) {
-    a=env->head->item->content.i;
+  if(CAR(env->head)->type==integer
+     && CAR(CDR(env->head))->type==integer) {
+    a= CAR(env->head)->content.i;
     toss(env); if(env->err) return;
-    b=env->head->item->content.i;
+    b= CAR(env->head)->content.i;
     toss(env); if(env->err) return;
     push_int(env, b*a);
 
     return;
   }
 
-  if(env->head->item->type==tfloat
-     && env->head->next->item->type==tfloat) {
-    fa= env->head->item->content.f;
+  if(CAR(env->head)->type==tfloat
+     && CAR(CDR(env->head))->type==tfloat) {
+    fa= CAR(env->head)->content.f;
     toss(env); if(env->err) return;
-    fb= env->head->item->content.f;
+    fb= CAR(env->head)->content.f;
     toss(env); if(env->err) return;
     push_float(env, fb*fa);
     
     return;
   }
 
-  if(env->head->item->type==tfloat
-     && env->head->next->item->type==integer) {
-    fa= env->head->item->content.f;
+  if(CAR(env->head)->type==tfloat
+     && CAR(CDR(env->head))->type==integer) {
+    fa= CAR(env->head)->content.f;
     toss(env); if(env->err) return;
-    b= env->head->item->content.i;
+    b= CAR(env->head)->content.i;
     toss(env); if(env->err) return;
     push_float(env, b*fa);
     
     return;
   }
 
-  if(env->head->item->type==integer
-     && env->head->next->item->type==tfloat) {
-    a= env->head->item->content.i;
+  if(CAR(env->head)->type==integer
+     && CAR(CDR(env->head))->type==tfloat) {
+    a= CAR(env->head)->content.i;
     toss(env); if(env->err) return;
-    fb= env->head->item->content.f;
+    fb= CAR(env->head)->content.f;
     toss(env); if(env->err) return;
     push_float(env, fb*a);
 
@@ -2099,7 +2060,7 @@
   }
 
   printerr("Bad Argument Type");
-  env->err=2;
+  env->err= 2;
 }
 
 /* "/" */
@@ -2108,50 +2069,50 @@
   int a, b;
   float fa, fb;
 
-  if((env->head)==NULL || env->head->next==NULL) {
+  if(env->head==NULL || CDR(env->head)==NULL) {
     printerr("Too Few Arguments");
-    env->err=1;
+    env->err= 1;
     return;
   }
   
-  if(env->head->item->type==integer
-     && env->head->next->item->type==integer) {
-    a=env->head->item->content.i;
+  if(CAR(env->head)->type==integer
+     && CAR(CDR(env->head))->type==integer) {
+    a= CAR(env->head)->content.i;
     toss(env); if(env->err) return;
-    b=env->head->item->content.i;
+    b= CAR(env->head)->content.i;
     toss(env); if(env->err) return;
     push_float(env, b/a);
 
     return;
   }
 
-  if(env->head->item->type==tfloat
-     && env->head->next->item->type==tfloat) {
-    fa= env->head->item->content.f;
+  if(CAR(env->head)->type==tfloat
+     && CAR(CDR(env->head))->type==tfloat) {
+    fa= CAR(env->head)->content.f;
     toss(env); if(env->err) return;
-    fb= env->head->item->content.f;
+    fb= CAR(env->head)->content.f;
     toss(env); if(env->err) return;
     push_float(env, fb/fa);
     
     return;
   }
 
-  if(env->head->item->type==tfloat
-     && env->head->next->item->type==integer) {
-    fa= env->head->item->content.f;
+  if(CAR(env->head)->type==tfloat
+     && CAR(CDR(env->head))->type==integer) {
+    fa= CAR(env->head)->content.f;
     toss(env); if(env->err) return;
-    b= env->head->item->content.i;
+    b= CAR(env->head)->content.i;
     toss(env); if(env->err) return;
     push_float(env, b/fa);
     
     return;
   }
 
-  if(env->head->item->type==integer
-     && env->head->next->item->type==tfloat) {
-    a= env->head->item->content.i;
+  if(CAR(env->head)->type==integer
+     && CAR(CDR(env->head))->type==tfloat) {
+    a= CAR(env->head)->content.i;
     toss(env); if(env->err) return;
-    fb= env->head->item->content.f;
+    fb= CAR(env->head)->content.f;
     toss(env); if(env->err) return;
     push_float(env, fb/a);
 
@@ -2159,7 +2120,7 @@
   }
 
   printerr("Bad Argument Type");
-  env->err=2;
+  env->err= 2;
 }
 
 /* "mod" */
@@ -2167,17 +2128,17 @@
 {
   int a, b;
 
-  if((env->head)==NULL || env->head->next==NULL) {
+  if(env->head==NULL || CDR(env->head)==NULL) {
     printerr("Too Few Arguments");
     env->err= 1;
     return;
   }
   
-  if(env->head->item->type==integer
-     && env->head->next->item->type==integer) {
-    a= env->head->item->content.i;
+  if(CAR(env->head)->type==integer
+     && CAR(CDR(env->head))->type==integer) {
+    a= CAR(env->head)->content.i;
     toss(env); if(env->err) return;
-    b= env->head->item->content.i;
+    b= CAR(env->head)->content.i;
     toss(env); if(env->err) return;
     push_int(env, b%a);
 
@@ -2185,7 +2146,7 @@
   }
 
   printerr("Bad Argument Type");
-  env->err=2;
+  env->err= 2;
 }
 
 /* "div" */
@@ -2193,17 +2154,17 @@
 {
   int a, b;
   
-  if((env->head)==NULL || env->head->next==NULL) {
+  if(env->head==NULL || CDR(env->head)==NULL) {
     printerr("Too Few Arguments");
     env->err= 1;
     return;
   }
 
-  if(env->head->item->type==integer
-     && env->head->next->item->type==integer) {
-    a= env->head->item->content.i;
+  if(CAR(env->head)->type==integer
+     && CAR(CDR(env->head))->type==integer) {
+    a= CAR(env->head)->content.i;
     toss(env); if(env->err) return;
-    b= env->head->item->content.i;
+    b= CAR(env->head)->content.i;
     toss(env); if(env->err) return;
     push_int(env, (int)b/a);